Achieving High‐Quality Freshwater from a Self‐Sustainable Integrated Solar Redox‐Flow Desalination Device

Abstract

As predicted by the International Energy Agency, our planet faces an energy and water crisis in the next 20 years. [1] Human demand for energy and water continues to increase, but the amounts produced are insufficient to meet consumption. [2][3][4][5][6] The ocean is a huge water source, and freshwater can be obtained by salt removal from seawater, which can be performed via two major commercial techniques: thermal distillation and membrane processing. [7][8][9][10][11][12][13][14] The thermal-based desalination techniques include multi-stage distillation, multieffect distillation, and vapor compression, all of which consume tremendous amounts of thermal energy. For example, the total energy consumption of a multistage flash evaporation process is in the range of 50-100 kWh m −3 to achieve highquality water production. [8,15] This makes it only suitable for specific areas with abundant thermal energy sources. Membrane-based desalination includes reverse osmosis and electrodialysis processes. [11,[16][17][18] Using these techniques can reduce energy consumption to <10 kWh m −3 with an output water quality with a salt content of <500 ppm. [8,19,20] In this regard, special attention has been paid to energy and water demand by the research community. [21][22][23][24] These issues have led to the development of a new technique in which renewable energy and desalination technologies are externally coupled to minimize energy consumption. [25] In contrast to the above techniques, electrochemical desalination has become a promising and versatile method that offers dual roles of desalination and energy storage simultaneously. [26][27][28][29][30][31][32][33][34] It removes salt ions through electrode-based reactions either by physical adsorption (capacitive deionization or nonfaradaic processes) or chemical reaction processes (battery desalination or faradaic processes). Meanwhile, the photoelectrochemical process technology becomes a crucial part for the environmental remediation, for instance: the process of water splitting by photoelectrochemical method paves a new way to reduce energy consumption. [35][36][37] Similarly, to achieve a zero-energy consumption process, photoelectrochemical desalination technology has recently been introduced. [38,39] In addition, another concept of solar desalination has been extensively studied: solar thermal desalination. In solar thermal Solar-assisted electrochemical desalination has offered a new energy-water nexus technology for sustainable development in recent studies. However, only a few reports have demonstrated insufficient photocurrent, a low salt removal rate, and poor stability. In this study, a high-quality freshwater level of 5-10 ppm (from an initial feed of 10 000 ppm), an enhanced salt removal rate (217.8 µg cm −2 min −1 of NaCl), and improved cycling and long-term stability are achieved by integrating dye-sensitized solar cells (DSSCs) and redox-flow desalination (RFD) under light irradiation without additional electrical energy consumption. The DSSC redox electrolyte ...

High-Performance Photoelectrochemical Desalination Based on the Dye-Sensitized Bi2O3 Anode

“…This salt removal rate is slightly higher, which is higher than that in the previous reports, 53,61 but lower than that using TiO 2 /N719 as a photoanode. 39 It was demonstrated that the technique of employing Bi 2 O 3 /N719 as the photoanode and AC electrode as the intermediate and counter electrodes in this device is successful and that quick salt removal is achievable with the availability of light.…”

Continuous Solar Desalination of Brackish Water via a Monolithically Integrated Redox Flow Device

“… a Initial short-circuit current density at illumination intensity of 150 mW (ref ), 153 mW cm –2 (ref ), 108 mW cm –2 (ref ), 140 mW (ref ), and 100 mW cm –2 (this work), respectively. b I 3 – /I – (redox 1) for DSSC and [Fe­(CN) 6 ] 3–/4– (redox 2) for RFD unit. …”

“…While previous solar RFD studies − demonstrated the feasibility of water desalination driven by sunlight and redox couples, there are some aspects that need further consideration. Either the photocurrent generated in the process was insufficient to produce freshwater, , or an unintegrated DSSC was used to power an RFD system, by externally connecting the two devices. , More importantly, the previously reported systems were operated in a closed-loop mode by recycling the diluate stream several times.…”

“…While previous solar RFD studies − demonstrated the feasibility of water desalination driven by sunlight and redox couples, there are some aspects that need further consideration. Either the photocurrent generated in the process was insufficient to produce freshwater, , or an unintegrated DSSC was used to power an RFD system, by externally connecting the two devices. , More importantly, the previously reported systems were operated in a closed-loop mode by recycling the diluate stream several times. Practical desalination processes that require the production of freshwater at high-throughput productivities would benefit from a single-pass continuous operation.…”

Efficient PEDOT Electrode Architecture for Continuous Redox-Flow Desalination

“…Upon optimization of PEDOT electrodes grown with different cycles, the electrocatalytic activity is enhanced. Since the PEDOT increased the capacitive behavior, the electrochemically active surface reaction induces the redox reaction of the [Fe­(CN 6 )] 3/4– species ,− (Figure S2a). The electrocatalytic activity is gradually increased for the PEDOT samples prepared at 5, 10, and 15 cycles.…”